1) Field of the Invention
The present invention relates to polishing abrasive grains, a polishing agent and a polishing method for use in polishing the surfaces of substrates, particularly semiconductor substrates, so called "bare wafers", and more particularly semiconductor device substrates. The term "semiconductor device substrates" used herein means substrates with a deposited thin film or films including a thin oxide film and a thin metallic film and/or a printed wiring thereon.
2) Description of the Related Art
According to the conventional polishing method, polishing, typically mirror polishing, of semiconductor device substrate surface is carried out by first supplying a polishing agent onto a polishing cloth-mounted table, and then pressing a substrate mounted on a support plate onto the turning or oscillating table with an appropriate pressing force, thereby polishing and flattening the substrate surface. Then, the polished substrate surface is cleaned to remove grains, particularly polishing abrasive grains of the polishing agent remaining on the substrate surface.
To remove metallic contamination, for example, due to metallic impurities originating from the polishing equipment, polishing cloth, polishing agent, etc. from the polished substrate surface after the polishing, at least following 4 steps are required:
1) Mechanical cleaning by brushing to remove fine grains remaining on the polished substrate surface after the polishing, PA1 2) Cleaning with an alkaline solution to further completely remove the fine grains from the polished substrate surface, PA1 3) Cleaning with an acid solution or chelating agent to remove metallic contamination from the polished substrate surface, and PA1 4) Precleaning of the polished substrate surface for successive steps.
In the above-mentioned conventional polishing method, the polished substrate must be subjected to at least said four cleaning steps 1) to 4) to remove metallic contamination from the polished substrate surface. In some cases, each of the cleaning steps must be carried out repeatedly, depending upon cleaning conditions, with the result of much increased cleaning runs. Sometimes, cleaning with a very dilute acid solution may be required, as in a case of polished semiconductor device substrates with printed aluminum (alloy) wirings on the surfaces, where such problems as corrosion of the wirings are always involved with the result of inevitable yield deterioration.
Without the cleaning with a cleaning solution having an adverse corrosive effect on the printed aluminum wirings to avoid the corrosion of wirings, on other hand, another problem such as failure to remove the metallic contamination caused mainly by the remaining polishing abrasive grains from the substrate surface will be involved.
U.S. Pat. No. 4,968,381 discloses a polishing method using a polishing agent containing at least one polar compound having hydrophilic and hydrophobic groups selected from the group consisting of alcohols, ketones, ethers, esters and amides, such as diethyleneglycol diethylether or diethyleneglycol dimethyl ether as an additive at the final phase of the polishing process.
JP-A 2-275629 discloses a polishing method for rinse-polishing a semiconductor device substrate with a diluted solution of an oxidizing agent such as sodium peroxide, sodium chlorate, hydrogen peroxide, ozone, etc. just before the completion of polishing, thereby making the semiconductor device substrate surface hydrophilic.
JP-A 7-235519 discloses a polishing method using a liquid mixture of hydrobromic acid, glycerine and water as a polishing agent, thereby making the semiconductor device substrate surface hydrophilic after the final polishing.
JP-A 8-22970 discloses a polishing method using a polishing agent containing an organic compound having at least one hydrophilic group such as carboxyl group, sulfor group, etc. and a molecular weight of at least 100, such as polymeric ammonium polycarboxylate and polymeric ammonium polysulfonate, thereby preventing dishing.
Furthermore, high purity amorphous silica fine powder produced by sol-gel process using alkoxysilane as starting material [e.g. Quatron colloid (PL series), trademark of products made by Fuso Siltech Co., Ltd., Japan], and synthetic silica fine powder showing a lipophilic property upon alkyl modification [e.g. Quatron water-repellent fine powder (WR series), trademark of products made by Fuso Siltech K.K., Japan] are now commercially available. Uses of PL series include, for example, not only a polishing agent for semiconductor device substrates but also fillers for various coatings and synthetic glass materials.